Signal isolation device and method for improving the same

Abstract

A signal isolation device includes at least one electromagnetic band-gap unit. The at least one electromagnetic band-gap unit includes a substrate, a metal foil main body, and a plurality of T-shaped metal foil features. The metal foil main body is disposed on the substrate, and the metal foil main body is square. The T-shaped metal foil features is disposed on the substrate and extending from a periphery of the metal foil main body. The T-shaped metal foil features are in a rotational symmetry around a center of the metal foil main body.

What is claimed is: 
     
         1 . A method for improving a signal isolation device, comprising:
 providing a signal isolation device which includes a plurality of electromagnetic band-gap (EBG) units adjoining each other, and each EBG unit has a substrate, a metal foil main body, and a plurality of metal features, the metal foil main body and the metal features are disposed on the substrate, and the metal features extend from a periphery of the metal foil main body;   generating a current concentration location related to the EBG units according to a corresponding frequency band of an insertion loss value of the signal isolation device;   determining that the signal isolation device has a capacitive property or an inductive property according to the corresponding frequency band of the insertion loss value; and   adjusting at least one of the metal features according to the current concentration location and according to the capacitive property or the inductive property of the signal isolation device.   
     
     
         2 . The method of  claim 1 , wherein the signal isolation device has the capacitive property, and adjusting the metal features includes adding a spiral path to one of the metal features. 
     
     
         3 . The method of  claim 2 , wherein the spiral path extends spirally from a center of the spiral path to an outward direction. 
     
     
         4 . The method of  claim 1 , wherein the signal isolation device has the inductive property, and adjusting the metal features includes adding an extension path, a portion of the extension path which is spaced apart from the metal foil main body extends along a periphery of the metal foil main body. 
     
     
         5 . The method of  claim 4 , wherein the portion of the extension path horizontally and straightly extends with respect to the periphery of the metal foil main body. 
     
     
         6 . A signal isolation device, comprising:
 at least one electromagnetic band-gap unit, comprising:
 a substrate; 
 a metal foil main body disposed on the substrate, and the metal foil main body is square; and 
 a plurality of T-shaped metal foil features disposed on the substrate and extending from a periphery of the metal foil main body, wherein the T-shaped metal foil features are in a rotational symmetry around a center of the metal foil main body. 
   
     
     
         7 . The signal isolation device of  claim 6 , wherein each T-shaped metal foil feature comprises a middle shaft portion, a first lateral portion, and a second lateral portion, wherein the middle shaft portion is disposed between the first lateral portion and the second lateral portion, the first lateral portion has a first length with respect to the middle shaft portion greater than a second length of the second lateral portion with respect to the middle shaft portion. 
     
     
         8 . The signal isolation device of  claim 7 , wherein a ratio of the first length to a side length of the metal foil main body is between 0.45 and 0.58. 
     
     
         9 . The signal isolation device of  claim 8 , wherein another ratio of the second length to the side length of the metal foil main body is between 0.1 and 0.3. 
     
     
         10 . The signal isolation device of  claim 6 , wherein the substrate is square and has a side length ranging from 7 mm to 25 mm. 
     
     
         11 . The signal isolation device of  claim 6 , wherein the metal foil main body has a side length ranging from 5 mm to 20 mm. 
     
     
         12 . The signal isolation device of  claim 6 , wherein the metal foil main body has a side length smaller than a side length of the substrate which is square. 
     
     
         13 . The signal isolation device of  claim 6 , wherein the at least one electromagnetic band-gap unit comprises a plurality of electromagnetic band-gap units which are arranged in a straight raw, one of the T-shaped metal foil features of one of the electromagnetic band-gap units joins one of the T-shaped metal foil features of another one of the electromagnetic band-gap units. 
     
     
         14 . The signal isolation device of  claim 6 , wherein the at least one electromagnetic band-gap unit comprises a plurality of electromagnetic band-gap units which are arranged in a straight raw, one of the T-shaped metal foil features of one of the electromagnetic band-gap units is in direct contact with one of the T-shaped metal foil features of another one of the electromagnetic band-gap units. 
     
     
         15 . A signal isolation device, comprising:
 a plurality of electromagnetic band-gap units arranged in a row, and each electromagnetic band-gap unit comprising:
 a square substrate; 
 a square metal foil main body disposed on the substrate; and 
 a plurality of T-shaped metal foil features disposed on the substrate and extending from a periphery of the metal foil main body, wherein the T-shaped metal foil features are in a rotational symmetry around a center of the metal foil main body. 
   
     
     
         16 . The signal isolation device of  claim 15 , wherein each T-shaped metal foil feature comprises a middle shaft portion, a first lateral portion, and a second lateral portion, wherein the middle shaft portion is disposed between the first lateral portion and the second lateral portion, the first lateral portion has a first length with respect to the middle shaft portion greater than a second length of the second lateral portion with respect to the middle shaft portion. 
     
     
         17 . The signal isolation device of  claim 16 , wherein a ratio of the first length to a side length of the metal foil main body is between 0.45 and 0.58. 
     
     
         18 . The signal isolation device of  claim 17 , wherein another ratio of the second length to the side length of the metal foil main body is between 0.1 and 0.3. 
     
     
         19 . The signal isolation device of  claim 15 , wherein the substrate has a side length ranging from 7 mm to 25 mm. 
     
     
         20 . The signal isolation device of  claim 15 , wherein the metal foil main body has a side length smaller than a side length of the substrate.